The Dual Endothelin-1/Angiotensin II Receptor (Dear) was originally isolated from an adult rat brain cDNA library using an AngII antisense oligonucleotide probe and also, independently, with an ET-1 oligonucleotide, see Molecular Medicine 4: 96-108, 1998. Structural analysis of the receptor revealed putative single predicted transmembrane domain and distinct ET-1 and AngII putative binding domains. Functional analysis has shown that both ET-1 and AngII bind to Dear and induce coupling to a Ca2+ mobilizing transduction system.
ET-1 is a potent vasoconstrictor peptide involved in diverse physiological functions such as blood pressure regulation, mitogenesis and apoptosis (Lariviere, R. et al. Can J Physiol Pharmacol. 81, 607-621 (2003), and angiogenesis (Salani, D. et al. Am. J. Pathol. 157, 1537-1547 (2000); Sullivan, D. C. & Bicknell, R. British Journal of Cancer 89, 228-231 (2003)), and has been implicated in several pathophysiological conditions such as hypertension, cardiac failure (Lariviere, R. et al. Can J Physiol Pharmacol. 81, 607-621 (2003); Ikeda, T. et al. Hypertension 34, 514-519 (1999); Touyz, R. M. & Schiffrin, E. L. Can J Physiol Pharmacol. 81, 533-541 (2003)), and more recently tumor angiogenesis, invasion and metastases (Bagnato, A. & Spinella, F. Trends in Endocrinology and Metabolism 14, 44-50 (2002); Grant, K., Loizidou, M. & Taylor, I. British Journal of Cancer 88, 163-166 (2003)).
AngII exhibits similar physiological responses to ET-1, such as blood pressure regulation, proliferation, apoptosis and angiogenesis (Watanabe, T. et al. Hypertension 45, 163-169 (2005), and has also been implicated in tumor angiogenesis (Escobar, E. et al. Curr Vasc Pharmacol 2, 385-399 (2004)). Separate receptors have been identified for binding by either ET-1 or AngII which are believed to be responsible for the physiological responses observed.
Accordingly, despite known roles for ET-1 and AngII, the role of Dear is currently unknown. It is believed that Dear regulates pathways distinct from those triggered by either ET-1 or AngII binding to ETA, ETB or AT1 and AT2 receptors respectively. However, due to its ability to bind to both ET-1 and AngII, and the important role these molecules play in angiogenesis, hypertension and tumor progression, a better understanding of Dear's role is needed. The present invention discloses newly discovered roles for Dear and presents methods to screen for, diagnose, prognose and treat various diseases and disorders such as hypertension, pathological angiogenesis and tumor growth/metastasis.
The genomes of all organisms undergo spontaneous mutation in the course of their continuing evolution, generating variant forms of progenitor genetic sequences (Gusella, Ann. Rev. Biochem. 55, 831-854 (1986)). A variant form may confer an evolutionary advantage or disadvantage relative to a progenitor form or may be neutral. In some instances, a variant form confers an evolutionary advantage to the species and is eventually incorporated into the DNA of many or most members of the species and effectively becomes the progenitor form. However, often times the variant form confers a disadvantage that may make an individual susceptible to certain diseases or disorders. An understanding of these variants may provide for better diagnosis of existing diseases or disorders, prognosis of the risk of obtaining certain diseases or disorders, and improved, more targeted treatments.
The knowledge of specific mutations and/or polymorphisms that are disease or disorder associated help identify patients most suited to therapy with particular pharmaceutical agents (this is often termed “pharmacogenetics”). Pharmacogenetics can also be used in pharmaceutical research to assist the drug selection process. Polymorphisms are used in mapping the human genome and to elucidate the genetic component of diseases. The following references show background details on pharmacogenetics and other uses of polymorphism detection: Linder et al. (1997), Clinical Chemistry, 43, 254; Marshall (1997), Nature Biotechnology, 15, 1249; International Patent Application WO 97/40462, Spectra Biomedical; and Schafer et al. (1998), Nature Biotechnology, 16, 33.
I. Hypertension
Hypertension, or high blood pressure, is the most common chronic illness in America. The American Heart Association estimates that more than 62 million Americans over the age of six suffer from high blood pressure, and that only a minority of these people have their blood pressure under control. Left untreated, hypertension can lead to stroke, heart attack, kidney damage, congestive heart failure, and death. Uncontrolled mild-to-moderate hypertension will reduce the life expectancy of a typical 35-year-old person by 16 years. Even the mildest form of high blood pressure, “borderline hypertension,” can cut one's life span by a few years and impact negatively on the quality of life.
The existence of a genetic component to hypertension is known from twin studies, which have revealed a greater concordance of blood pressure in monozygotic twins than in dizygotic twins. Similarly, biological siblings show greater concordance of blood pressure than adoptive siblings raised in the same household. Such studies have suggested that up to about 40% of the variations in blood pressure in the population are genetically determined. However, to date, a reliable genetic marker for hypertension has not been identified. Although significant gains have been made with respect to treatment, hypertension prevails as a major risk factor for heart and kidney disease, and stroke prompting the lowering of the BP level at which to start treatment.
Thus, a genetic marker for predicting one's susceptibility to hypertension is needed, as well as, a reliable method to diagnose hypertension is needed. Additionally, treatment strategies targeting the normalization of mutant genes contributing to genetic hypertension (hypertension genes) are needed.
II. Angiogenesis
Angiogenesis is a process of tissue vascularization that involves both the growth of new developing blood vessels into a tissue (neo-vascularization) and co-opting of existing blood vessels to a target site. Blood vessels are the means by which oxygen and nutrients are supplied to living tissues and waste products are removed from living tissue. Angiogenesis can be a critical biological process. For example, angiogenesis is essential in reproduction, development and wound repair. Conversely, inappropriate angiogenesis can have severe negative consequences. For example, it is only after solid tumors are vascularized as a result of angiogenesis that the tumors have a sufficient supply of oxygen and nutrients that permit it to grow rapidly and metastasize.
Angiogenesis-dependent diseases and disorders are those diseases and disorders affected by vascular growth. Such diseases represent a significant portion of diseases for which medical treatment is sought, and include inflammatory disorders such as immune and non-immune inflammation, chronic articular rheumatism and psoriasis, disorders associated with inappropriate or inopportune invasion of vessels such as diabetic retinopathy, macular degeneration, neovascular glaucoma, restenosis, capillary proliferation in atherosclerotic plaques and osteoporosis, and cancer associated disorders, such as solid tumors, solid tumor metastases, angiofibromas, retrolental fibroplasia, hemangiomas, Kaposi sarcoma, cancers which require neovascularization to support tumor growth, etc.
While methods to inhibit unwanted angiogenesis are known, few have proven clinically useful. For example, a number of therapeutic strategies exist for inhibiting aberrant angiogenesis, which attempt to reduce the production or effect of VEGF. For example, anti-VEGF or VEGF receptor antibodies (Kim E S et al. (2002), PNAS USA 99: 11399-11404), and soluble VEGF “traps” which compete with endothelial cell receptors for VEGF binding (Holash J et al. (2002), PNAS USA 99: 11393-11398) have been developed. Classical VEGF “antisense” or aptamer therapies directed against VEGF gene expression have also been proposed (U.S. published application 2001/0021772 of Uhlmann et al.). The anti-angiogenic agents used in these and similar non-VEGF targeted therapies have typically been unsuccessful. The results achieved with available anti-angiogenic therapies have therefore been generally unsatisfactory.
Thus, methods to reduce or eliminate unwanted angiogenesis are needed.
Conversely, in situations where angiogenesis is desired, such as, for example, reproduction, development, wound repair and areas of ischemia or infarction, the stimulation of angiogenesis is useful. Current methods to initiate or up-regulate angiogenesis have also typically been clinically unsuccessful and are thus needed.
Furthermore, because ET-1 is also associated with breast cancer growth and pro-malignant potential, inhibition of Dear will also be useful in decreasing tumor growth and potential to metastasize, independent of its effects on angiogenesis.